1. Field
The present disclosure relates to an article having an anti abrasion layer, comprising a mixture of irregular particles of hard material and round particles of solid material, essentially free of cutting edges, embedded in a matrix material having a substrate and an anti-abrasion layer on the surface of the substrate, in which the substrate is selected from wood materials, decorative papers and wood fibre sheets printed with patterns, and the anti abrasion layer, and the use thereof for the production of wear-resistant surfaces on wood materials, decorative papers, or wood fiber sheets printed with patterns for the production of parquet flooring, laminate flooring, furniture surfaces or work boards, and for the production of wear-resistant surface layers on substrate materials made from metal, glass, ceramic, plastic, concrete or other materials, for the production of tile glazes for coating tiles, and for the production of enamel for metal containers or reactors for the chemicals industry, but also for household appliances and faucets.
2. Background
The process of sealing surfaces of furniture, floors, ceramics, or wear surfaces in general made of a wide variety of materials in order to both protect the surface and give it a decorative appearance is generally known. A very wide variety of matrix materials are used for this purpose, which serve to decrease the sensitivity of the surface to mechanical, thermal or chemical stresses, while simultaneously giving it a decorative look. Frequently, the matrix materials are duroplastic, thermoplastic or elastomeric plastics, which can be hardened under the effects of temperature or radiation.
The surfaces of furniture and floors in particular are frequently exposed to very heavy mechanical stresses, and must be protected accordingly.
Also generally known is the process of providing the surfaces of furniture, flooring, etc. with a decorative appearance by applying so-called high-pressure laminates. In this case, the laminate is frequently comprised of three different layers, a colored or printed decorative paper, a transparent overlay paper on top of this, and a plurality of so-called core papers underneath this, which serve as the substrate for the decorative paper and the overlay paper. Usually, all three papers are impregnated with a hand is thermoset directly onto a wood fiber sheet, and a process is known in which the pattern is printed directly onto a pretreated and primed wood fiber sheet, after which the surface is coated with a clear lacquer which has an acrylate base and is filled with hard aluminum oxide material, and is then radiation hardened.
Substances that are particularly suitable as thermosetting and/or radiation hardenable synthetic resins or lacquer systems include phenolic resins, acrylate resins, epoxy resins, polyester resins, melamine resins, aminoplastics, polyurethanes, and mixtures of these components. In the past, repeated attempts have been made to increase the abrasion resistance of a laminate by embedding particles of hard material in the resin layer with which a core-impregnated decorative paper will be covered, for example.
For instance, several publications and patents describe corresponding methods for producing abrasion-resistant decorative layers or laminates, in which especially particles having an aluminum oxide base are listed as suitable hard material particles for the production of wear-resistant decorative layers. In this case, the preferred range for the average size of these particles lies between 1 and 80 μm.
For instance, U.S. Pat. No. 3,928,706 A describes the production of abrasion-resistant decorative layers which consist of a core paper, a decorative paper, a wear layer and an overlay paper. The wear layer, consisting of a thermosetting synthetic resin with hard materials distributed finely throughout and having a Mohs hardness rating of at least 7, is applied to a surface of either the decorative paper or the overlay paper. All three papers are impregnated with a thermosetting synthetic resin and are processed in the customary manner to a uniformed laminate, in which they are pressed between highly polished pressing plates at temperatures of approx. 150° C.
EP 0 519 242 A1 describes anti abrasion layers of particular clarity and brilliance, which are obtained by providing the decorative paper with a wear layer which contains hard materials sheathed with silane. In this case as well, processing to a finished laminate is achieved via pressing.
In all cases, the production of wear-resistant laminate surfaces by embedding hard materials in overlay or decorative paper or through direct coating with liquid overlays filled with hard materials results in a significant problem in the ultimate production of the laminates, because both with batch operation using presses with highly polished pressing plates, and with continuous operation using pressing belts, the surfaces of the pressing plates or pressing belts are scratched by contact with the particles of hard material, rendering them unusable relatively quickly. This pressing plate wear represents a very significant cost factor in the production of wear-resistant decorative layers.
Attempts to solve the problem of wear during production have in most cases involved employing suitable measures to prevent direct contact between the particles of hard material and the pressing plates.
For instance, WO 2006/013469 describes a method in which a first polymeric layer, which contains particles of hard material, such as corundum, for example, is first applied to a substrate, and then a second polymeric layer, in which particles are embedded which have a relatively high hardness rating but low abrasiveness, is applied to this first abrasion-resistant layer. Particles of this type include glass beads or glass fibers, for example.
A similar method is described by EP 1 319 524 A1, in which the object is attained by using lacquer or impregnating resin systems that contain beads, especially glass beads, which have a relatively high hardness rating but low inherent abrasiveness. In this case, the use of actual hard materials is dispensed with entirely.
In WO 02/066265 A1, a method of producing a decorative paper is described in which abrasion-resistant particles, such as corundum or silicon carbide, for example, which are embedded in the resin, are coated in an additional process step with glass beads or glass fibers, in order thereby to prevent the corundum or silicon carbide particles from coming into direct contact with the reflective surface of the press and damaging it. The beads or fibers are thus intended to ensure the desired protective spacing between the abrasion-resistant particles and the pressing plate or pressing belt.
EP 1 339 545 B1 describes an anti abrasion layer with an synthetic resin base, wherein, in addition to the particles of hard material having a Mohs hardness rating of at least 6, round, solid material particles in the form of beads that are essentially free of cutting edges are embedded in the synthetic resin system, said beads having a low hardness rating and an average particle diameter that is greater than the average particle diameter of the particles of hard material. In this manner, direct contact between the pressing plate surface and the particles of hard material is largely prevented, and the round solid material particles serve quasi as spacers.
All of these methods have the disadvantage, however, that in the outer area of the decorative layer, rather than particles of hard material, particles of lower hardness are contained, thereby decreasing the wear-resistance of the layer overall.
Precisely in the area of flooring or laminate flooring, especially in public buildings or industrial facilities, but also on surfaces of furniture or working boards that are subject to frequent use, wear-resistance plays an increasingly greater role, and is used as a very convincing sales argument and criterion for quality. For example, laminate sheets are subjected to abrasion classification, wherein in a so-called “Taber test” the resistance to abrasion is determined, and the flooring is divided into abrasion classes. This test is used to determine the resistance of the cover layer to wear. Abrasion is achieved by rotating a test sample under stressed, cylindrical friction wheels covered with defined lubrication gel paper. The number of rotations necessary to produce a predetermined degree of abrasion is measured.
For this test, according to DIN EN 13329, test samples measuring approximately 100 mm×100 mm are taken from a laminate floor element and are divided into four quadrants using a marking pen. The surface of the test sample is processed under precisely defined conditions (pressure, rotation, etc.) with two friction wheels covered with a defined lubrication gel paper, wherein the strips of lubrication gel paper are replaced after every 200 rotations. This test is continued until a so-called initial abrasion point (IP) is reached. The initial abrasion point (IP) is the point at which abrasion through the decorative printing is clearly discernible for the first time, and the lower layer is exposed in three of the four quadrants. In this manner, laminate floors are divided into abrasion classes from AC 1 to AC 5, which corresponds to an IP value of ≧900 to ≧6000.